close

Вход

Забыли?

вход по аккаунту

?

Патент USA US2117835

код для вставки
May 17, 1938.
H. s. BLACK
2,117,835
TELEPHONE SIGNALÍNG SYSTEM
Original Filed June l, 1956
m.
und
,
2 Sheets-Sheet 1
_
m@ FLT;
_
mw
wmuw.BLU
A TTOR/VEV
May 17, 1938.
2,117,835
Y H. s. BLACK
TELEPHONE SIGNALING SYSTEM
Original Filed June l, 1956
2 Sheets-Sheet 2
.NN
QT@__
N@Fx
F
Db;
_ la»
_b
/NVENTOR
By
H. 5. BLACK
2,117,835
Patented May 17, 1938
UNITED sTATEs
PATENT oEEIcE
2,117,835 `
TELEPHONE SIGNALING srs'rEM
Harold S. Black, Elmhurst, N. Y., assignor to
Bell Telephone Laboratories, Incorporated, New
York, N. Y., a corporation of New` York
Application June 1,' 1936, Serial'No. 82,848
Renewed December 31, 1937` l
10 Claims.
This invention relates to telephone signaling
systems and particularly to the transmission of
low frequency signals, such as ringing signals, in
carrier telephone systems.
In carrier telephony, as practiced in the field
today, it is customary to associate with a tele
such areas the tuned circuit does not serve to
advantage.
It is, accordingly, the object of this invention
to simplify and improve low frequency signaling
facilities in carrier telephone systems and to ren
der such systems immune to frequency variations
phone line ìnterconnectingtwo widely separated
telephone exchanges, carrier equipment which
of the signaling current source.
This object is attained in accordance with a
renders it possible to utilize the line circuit for
the simultaneous transmission of a plurality of
telephone communications. In such systems, the
frequency discriminating means heretofore em
telephone line terminates at the two exchanges
in jacks, by virtue of which a connection between
calling and called subscribers may be completed
by way of the line circuit. -Superimposed on the
line at each end thereof is a jack-ended carrier
channel which comprises carrier terminal appa
ratus so designed as to vtransmit and receive
speech currents modulated at a particular car
20 rier frequency.
In certain systems of this type it is customary
to utilize 20-cycle -frequency alternating current
for the transmission of signals, other than speech
signals, between exchanges. Due to the trans
mission characteristics of the carrier terminal
equipment it is necessary that the low frequency
signaling current be excluded from the carrier
channel and transmitted over the physical line
circuit. Heretofore, the separation of the low
frequency signaling currents and the high fre
quency speech currents was accomplishd by
bridging the carrier channel, between the jack
terminals thereof and the carrier equipment, with
a low frequency tuned circuit including an in
' ductance coil vand a tuning condenser, and in
ductively coupling the bridge circuit with the
physical circuit. The bridge circuit presents a
high impedance to currents in the range of voice
frequencies and a relatively low impedance at
40 frequencies within the range of those used for
the transmission of ringing signals. I_n this man
ner the signaling currents of low frequencies have
4
(Cl. 179-84)
feature of the invention by substituting, for the
10
ployed in the low frequency signaling bridge as
sociated with carrier telephone lines, a voltage
discriminating device whose effective functioning
depends, not upon the constancy of the frequency
of the supply source, but upon the relative volt
ages of the signaling and speech currents im
pressed on the line, irrespective of their frequen
cies. More specifically, a resistor, such as a silver
sulphide resistor, having a characteristic such
that it presents a high resistance when subjected
to voltages below a certain critical value, is in
cluded in the signaling bridge associated with car
rier telphone lines.
The action of a silver sulphide resistor is such
that as the voltage applied is increased, the tem 25
perature of the resistor is increased until a criti
cal point is reached. At this point the resistance
suddenly drops to a very low value. Since the
heating of the resistor is a function of the voltage
applied, the resistance will drop to a low value 30
at a critical voltage. For this reason, reference
is made, hereinafter, to the silver sulphide resis
tor asa voltage discriminating device.
The voltage of the low frequency signaling
source used in these systems is, generally, in the
neighborhood of 95 to 115 volts and since, Vas is
well known, speech currents, when impressed on
a line circuit, produce relatively low voltages,
usually in the neighborhood of several volts, a re
sistor having a characteristic such as defined
above will serve satisfactorily as a means for
been effectively excluded from the carrier chan
nel and the voice frequencies transmitted there
separating the speech and signaling currents in
a carrier telephone system and will obviate the
need for such expensive equipment as the in
ductance coil and tuning condenser heretofore 45
over without interference.
used for this purpose.
Such an arrangement
has been found to function satisfactorily in all
instances where the frequency of the signaling
current source remained constant.
In numerous areas served by the telephone
50
operating companies, the source of low frequency
signaling current is known to vary in frequency
over relatively wide limits. In some localities,
the signaling frequency varies anywhere from
55 less than 15 cycles to more than 20 cycles. In
The invention will be readily understood from
the following detailed description made with ref
erence to the accompanying drawings in which:
'Figs 1 and 2, when placed side by side, .with
Fig. 1 at the left, show in schematic form a cir
cuit for superposing on an ordinary telephone
line L, a carrier telephone channel of the type
disclosed in U. S. Patent 1,983,528, issued Decem
ber l1, 1934 to H. S. Black, and in which a silver
2
2,117,835
sulphide resistor is included in the alternating
current signaling bridge in accordance with the
present invention.
line at the terminals of iack II'. In answering
this signal, the operator at station B would pro
ceed in the usual manner by inserting the an
'I'he ordinary or physical circuit is connected
to the line L at each of the exchanges A and B
through a low-pass filter I0 or Ill’ leading to a
jack II or II’. Thus the subscriber’s station I2
may be connected, for a toll call, by suitable local
swering plug of a cord I6’ into jack II' to open
the circuit to the drop signal 5I ' which is restored
to normal. A signal originating at station B is
transmitted to the station A in a similar man
ner to cause the actuation of drop signal 5I.
and toll board switching circuits, such as answer
ing jack I3, toll switching trunk I4 leading to
jack I 5 at the exchange A and toll cord I 6 to jack
On a call that is to be extended from station A
to station B by way of the line L and the carrier
channel associated therewith, the operator at sta
I I and thence to the line L. At the opposite ter
tion A inserts the calling plug of her cord 26 into
minal, or station B (Fig. 2) the call may be ex
the jack 3| to remove the drop signal 50 from
tended to the toll switching trunk I4' by way of the line and then actuates the ringing key 52.
the toll cord I6’ and eventually to the called sub
Ringing current from the 20-cycle source 53 is
scriber's station I2’ by way of jack I3’ located' thereupon impressed on the terminals of the car
at an ofllce at which the called line terminates.
rier channel and on the bridge circuit connected
In an analogous manner, the same subscriber’s
station I2, or for simplicity of description, an
other subscriber’s station 22 may be connected,
for a toll call, by jack 23, toll switching trunk 24,
jack 25, toll cord 26 and jack 3| to the carrier
terminal apparatus shown located between the
jack 3I and the line L. At the opposite termi
nal (Fig. 2), corresponding carrier terminal
equipment intervenes between the line L and
jack 3l', from whence the call may be extended
to a calling subscriber’s station 22' by way of the
jack 3I’, toll cord 26', jack 25', toll switching
30 trunk 24’ and line jack 23’.
'I'he carrier equipment, beginning at the jack
3I or low frequency terminals, comprises at each
station, a speech ñlter 32 or 32’ designed to pass
speech currents, but suppress currents of higher
frequencies, a modulator-demodulator circuit 33
or 33' and a high-pass filter 34 or 34' adapted to
pass currents of frequencies employed by the car
rier channel but excluding speech frequency cur
rents. Thus filters I0 and 34 serve to impress
40 separately on line L, or to receive from line L and
separate into their respective terminal branches,
the low frequency speech currents in the physi
cal branch and the high frequency carrier side
band currents in the carrier branch, respectively.
In addition to the elements mentioned, the sta
tion A has a source of carrier waves 40 and in some
cases preferably would have a phase compensat
ing network 44. It will be noted that the carrier
source is present at only one of the stations.
It is believed unnecessary to disclose in detail
50
the carrier terminal equipment since it is fully
shown and described in the above-identified pat
ent. Only that much of the equipment necessary
for a complete understanding of the invention is
55 shown in the drawings vin detail,
In order for the operator at station A to signal
an operator at station B on a call to be extended
over the physical branch of line L, the former
would actuate ringing key ‘II associated with the
60 toll cord I6 whereupon ZO-cycle signaling current
from the source 53' would be impressed on the tip
and ring conductors of the physical branch, as
suming of course, that the calling jack of the cord
I6 is inserted in the jack II, which causes the
65 drop signal 5I to be disconnected from the line.
Signaling current would therefore traverse the
left-hand winding of repeating coil 56 and would
be induced in the right-hand winding thereof,
from whence it would travel transversely over
70 the physical branch including the low-pass filter
III, line L, low-pass filter I0’ and through the left
hand winding of repeating coil 60. Signaling
current induced in the right-hand winding of
repeating coil 60 thereupon traverses the winding
of drop signal 5I’ which is connected -across the
thereacross which comprises the silver sulphide
resistance 54 and the primary of transformer 55.
Since the voltage of the signaling current source
is in the neighborhood of 90 to 116 volts, Well
above the critical value at which the resistor
breaks down, the resistance of the bridge circuit
is reduced materially with the result that the
carrier channel is, in eifect, short-circuited, and
the signaling current traverses the primary wind
ing of transformer 55. 'I‘he current induced in
the secondary of 55 travels from ground through
the secondary of 55, simplex leg 56 to the mid
point 51 of the right-hand winding of repeating :.f.
coil 58 and thence longitudinally over the physi
cal branch, line L, the other physical branch to
the mid-point 59 of the left-hand winding of re
peating coil 60 and thence to ground by way of the
simplex leg 6I and secondary of transformer 62. ..
Current is induced in the primary of 62 and
travels through drop signal 50’ by way of the silver
sulphide resistor 63 and the normally closed con
tacts of jack 3|'. The operation of drop signal
50’ indicates to the operator at station B that 40
there is a, call awaiting on the line identified by
the signal 50'. 'I'he operator answers the call
in the well known manner. Signaling current
from station B may be transmitted over the line
in a similar manner to actuate the drop signal 50
at station A.
The bridge circuit including the. resistors 54 or
63 presents a very high resistance to speech cur
rents since the voltages set up across this circuit
by these currents are very small and well below
the critical breakdown value. The speech cur
rents are accordingly impressed on the carrier
equipment unimpeded in any manner by the
bridge circuit. When the high voltage signaling
current, however, is impressed on the line at the
jack 3I, the silver sulphide breaks down and be
comes a low resistance causing the signaling cur
rent to be excluded from the carrier channel and
transmitted over the physical branch of line L.
It is apparent, from the foregoing, that the fre
60
quency of the signaling source, such as 53, may
vary Without, in any way, affecting the operation
of the system due to the inclusion, in the signal
ing bridge, of a resistor which functions inde
pendently of frequency and which relies solely
upon the relative voltages of the signaling and
speech currents in producing the desired results.
Silver sulphide, not only has the desired charac
teristics, but is considerably cheaper than the
tuned circuits heretofore employed.
What is claimed is:
1. In a telephone system, a line circuit includ
ing a physical branch and a carrier channel, and
means including a signaling bridge circuit cou~
pling the terminals of the carrier channel with 75
3
anneau '
7. In a telephone system, a line-circuit includ
the physical branch of said line circuit, said
bridge including a non-linear resistance.
2. In a telephone system, a line circuit includ
ing a physical branch and a carrier channel, and
means including a signaling bridge circuit cou
pling the terminals of the carrier channel with
the 'physical branch of said line circuit, said
bridge including a silver sulphide resistor.
3. In a telephone system, a line circuit includ
ing a physical branch and a carrier channel, said
carrier channel adapted for the transmission of
speech 'frequency currents, and means including
a bridge circuit coupling the terminals of the car
rier channel with the physical branch of said line
15 circuit, said bridge including a. resistor which
presents a high resistance to the speech frequen
cies impressed on said carrier channel.
4. In a telephone system, a line circuit includ
ing a physical branch and a carrier channel
20 adapted for the transmission of speech frequen
cies, a source of signaling current of higher volt
age than those of the speech frequencies trans
mitted over the carrier channel, and means in
cluding a bridge circuit coupling the terminals
of the carrier channel with the physical branch
of said line circuit, said bridge including means
which presents a high resistance at the voltage
of the speech currents and becomes a low resistance at the voltage of said signaling current
30
source.
`
ì
5. In a telephone system, a line circuit includ
ing a physical branch, a carrier channel associ
lated with said line circuit, a source of signaling
current, switching means for connecting said
source to said carrier channel, and a bridge cir
cuit connected across said carrier channel and
inductively associated with the physical branch of
said line, said bridge including a non-linear re
sistance which becomes effective upon the opera
tion oi said switching means in vexcluding current
40 from said source from the carrier channels and
causing it to be transmitted over the physical
branch of said line.
,
6. In a telephone system, a line circuit includ
ing a physical branch, a carrier channel associ
ated with said line circuit, a source ci signaling
current, switching means for connecting said
source to said carrier channel, and a bridge cir
cuit connected across said carrier channel and
inductively associated with the physical branch,
50 said bridge including a silver sulphide resistor
which becomes effective, upon the operation of
said switching means, in excluding current from
said source from said carrier channel and trans
mitting it over the physical branch oi.' said line
ing a physical branch, a carrier channel associ
ated with said line circuit, means for impressing
low voltage speech currents on said carrier chan
nel, means for impressing high voltage signaling
current on said carrier channel, and voltage dis
crlminatlng means connected across said car~
rier channel and inductively associated with the
physical branch of said line which serves to ex
clude the high voltage signaling current from 10
said carrier channel and cause it to be'trans
mitted over the physical branch, said discrimi
nating means eiîecting a high resistance shunt
across said channel when subjected to the low
15
voltage speech currents.
8. In a telephone system, a line circuit'includ
ing a physical branch, a carrier channel associ
ated with said line circuit, means for impressing
low voltage speech current on said carrier chan
nel means for impressing high voltage signaling 20
current on >said carrier channel, and a bridge
circuit connected across said carrier channel and
inductively associated with the physical branch
of said line, said bridge circuit including a. silver
sulphide resistor which presents a high’resistance
to the low voltage speech currents and becomes a
low resistance when subjected to the high voltage
signaling currents whereby said signaling cur
rents are excluded from said carrier channel and
transmitted over the physical branch of said line
and the speech currents are transmitted over said
carrier channel.
9. In a telephone system, a carrier channel
adapted to be subjected to high voltage signaling
and low voltage speech currents, and voltage dis
criminating` means connected across said car
rier channel for excluding the high voltage sig
naling current from said channel while permit
.ting the transmission of the low voltage speech
currents thereover, said means including a silver 40
sulphide resistor.
-
l0. In a telephone system, a carrier channel
adapted to be subjected to high voltage signaling
and low voltage speech currents, and means for
effectively short-circuiting said channel when
subjected to high voltage signaling current, said
means comprising a circuit in bridge of said
channel and including a resistor having a char
acteristic such that it presents a high resistance
when subjected to voltages produced by the 50
speech currents and a low resistance when sub
jected to voltages produced by the signaling Vcur
rents.
HAROLD S. BLACK.
66
Документ
Категория
Без категории
Просмотров
0
Размер файла
526 Кб
Теги
1/--страниц
Пожаловаться на содержимое документа